Resistor



Oct. 27, 1959 J. G. LANNING RESISTOR Filed Nov. 8, 1957 INVENTOR. Jan xvG ZA/WW/YG W /z &@

United States Patent RESISTOR John G. Lanning, Corning, N.Y., assignorto Corning Glass Works, Corning, N.Y., a corporation of New YorkApplication November 8, 1957, Serial No. 695,393

4 Claims. (Cl. 338-'300) The present invention relates to electricalresistance elements, and is primarily concerned with an improvement in aresistor of the type comprising a linear dielectric body supporting aspiral ribbon of resistance material along its length between bands oflow resistance material supported on the ends of such body and servingas the resistance element terminals.

Such form of resistor ordinarily comprises a circular rod of dielectricmaterial bearing a resistance element comprising a spiral ribbon ofcarbon, or of tin oxide or the like. To make such a resistor, a suitablycoated rod is conventionally placed in a lathe and spirally grooved sothat the coating material remaining is in the form of a spiral ribbonabout the body between the terminal bands of low resistance material.

It has been observed that such a resistor when operated at a currentdensity somewhat below the maximum calculated for it, that failureoccurs in localized regions in the margin of the coating adjoining oneor the other of the terminals.

From an invesigation made, by laying out such a ribbon and its terminalsin a flat plane, it has been discovered that the reason for such failureis that the outline of the ribbon between its terminals comprises arhomboid; thus the shortest path between the terminals is a straightline extending diagonally across such rhomboid between its wide anglecorners, resulting in high current concentration along such line at suchcorners. The exact regions of failure are thus pinpointed as being atsuch corners where the width of the coating is narrowest.

According to the invention the bands of low resistance material, servingas the resistor element or ribbon terminals, are extended transverselyof the ribbon ends at an angle of 90 so that the current between suchterminals is uniformly distributed throughout the ribbon width along itsentire length, thus enabling such ribbon to withstand a current densityin accordance with the ribbon width and its resistance per unit oflength.

For a better understanding of the invention reference is now made to theaccompanying drawing wherein:

Fig. 1 is side elevational view of a resistor of conventional form.

Fig. 2 is a diagrammatic view showing the ribbon coat- 2,910,664Patented Oct. 27, 1959 ing and terminals of a conventional form ofresistor laid out in a single plane.

Fig. 3 is a view corresponding to Fig. 2 when modified in accordancewith the invention.

Fig. 4 is a view, similar to Fig. 1, of a complete resistor embodyingthe invention.

In the resistor as shown in Fig. 1 the dielectric rod 11 bears lowresistance metal bands or terminals 12 and 13 at its ends with a coating14 of resistance material in ribbon form spiralled about such rodbetween such bands. As will be seen from Fig. 2, when the respectiveterminals 12 and 13 and the coating 14 are laid out in a single plane,the coating 14 takes the form of a rhomboid. Accordingly, the shortestpath between the terminals 12 and 13 is a line 20 drawn diagonally ofcoating 14 be tween the wide angled corners 21 and 22, resulting in highcurrent concentrations at such corners.

The above fault is overcome by, as indicated in Fig. 3, providing lowresistance terminals or bands such as 35 at each end of the ribboncoating 34, such bands extending transversely of the ribbon at a angle,as indicated, so that the space between the terminals is rectangular,thus aflfording a uniform current density flow path that embodies theentire width of the ribbon-like coating throughout its length.

What is claimed is:

1. An electrical resistor comprising a rod of dielectric material havingan electrically conductive coating thereon in the form of a ribbonspiralled thereabout along its length and having low resistanceterminals at the rod ends comprising coatings on the rod that unite withthe conductive ribbon along lines running at an angle of 90 with respectto its linear dimension.

2. An electrical resistor comprising a rod of dielectric material havingan electrically conductive coating thereon in the form of a rectangularribbon spiralled there about along its length, and low resistanceterminals comprising conductive coatings extending about such rod alongand in union with the ends of such ribbon.

3. An electrical resistor comprising a rod of dielectric material havingan electrically conductive coating thereon in the form of a ribbonspiralled thereabout along its length and having low resistanceterminals at the rod ends extending about such rods and that unite withthe conductive ribbon along lines perpendicular to its linear dimension.

4. An electrical resistor such as defined by claim 3 wherein the ends ofsuch rod are surrounded by portions of such terminals.

References Cited in the file of this patent UNITED STATES PATENTS2,044,678 Frese June 16, 1936 2,803,729 Kohring Aug. 20, 1951 FOREIGNPATENTS 501.971 Italy Nov. 26, 1954

